The advent of the Internet and the demand for bandwidth has created the need for telecommunications systems which are able to provide high speed digital connections to and from a subscriber""s residences. Because of the large amount of twisted wire pair cables which have been deployed for telephone service over many decades, there is a tremendous incentive to reuse these cables to provide high speed data services in addition to telephone services.
A number of techniques have been developed for transmitting high speed digital data signals over twisted wire pairs and include Integrated Digital Services Network (ISDN) technologies, Asymmetric Digital Subscriber Line (ADSL) technologies, Rate Adaptive Digital Subscriber Line (RADSL) technologies and Very High Speed Digital Subscriber Line (VDSL) technologies.
Of these technologies, VDSL provides the highest data rates to and from the subscriber, and can potentially provide data rates of 52 Mb/s over loop lengths of 3,000 ft. However, in transmitting such high speed signals over twisted wire pair, the loss is quite substantial and is not equal over the frequency range in which the signals are transmitted.
In addition, the loss depends heavily on the loop length, and it is not possible to use a constant slope amplifier to equalize the VDSL signal. Furthermore, the circuit that performs the equalization is typically located at the subscriber side of the network, and cannot easily be accessed by the network operator.
For the foregoing reasons, there is a need for a method and apparatus which provides for equalization and reliable reception of a VDSL signal.
In the present invention a Very High Speed Digital Subscriber Line (VDSL) signal is received from a twisted wire pair drop cable, and an equalization circuit provides additional gain in the high end of the VDSL band in order to compensate for the higher losses on the twisted wire pair at those frequencies.
In a preferred embodiment, the additional amplification is realized through the use of a resonator circuit. The resonator circuit can be switched in and out of the gain block using a field effect transistor.
In a preferred embodiment, a determination can be made as to whether the equalization is necessary, and the circuit selectively switched in or out depending on the results of the determination.
In a preferred embodiment the total power received is measured and a determination is made that the higher frequencies have been severely attenuated.
These and other features and objects of the invention will be more fully understood from the following detailed description of the preferred embodiments which should be read in light of the accompanying drawings.